Gameboy Development Forum

So, I figured gbt_player is great for background music, but for simple sound effects using just the registers is enough.
I've found some really handy snippets that break up the sound channels into something a human can understand and use.
I'm using this snippets to make some python preprocessor that spits out the final hex values so I don't use memory during the game.
There's more over here: http://justinkent.com/gbblocks/index.html

// channel 1/2
sweeptime = 7; /* 0-7 */
sweepmode = 1; /* 0-1 */
sweepshifts = 1; /* 0 - 7 */
patternduty = 1; /* 0-3 */
soundlength = 0; /* 0 - 63 */
envinit = 15; /* 0 - 15 */
envmode = 0; /* 0-1 */
envsteps = 2; /* 0 - 7 */
freql = 000;
freqh = 5;
consecutive = 0;
initialflag = 1;
NR10_REG = (sweepshifts + (sweepmode * 8) + (sweeptime * 16));
NR11_REG = (soundlength + (patternduty * 32));
NR12_REG = (envsteps + (envmode * 8) + (envinit * 16));
NR13_REG = freql;
NR14_REG = (freqh + (consecutive * 64) + (initialflag * 128));

Last edited by andreai (2014-10-20 08:18:18)

I made a thing that's a bit longer than that, but simplifies it a lot more.


#include <gb\gb.h>
#include <stdio.h>

int length = 250;

void E(){
NR12_REG = 0xF0;
NR13_REG = 0x00;
NR14_REG = 0x86;
delay(length);
NR12_REG = 0x00;
delay(50);
}

void F(){
NR12_REG = 0xF0;
NR13_REG = 0x28;
NR14_REG = 0x86;
delay(length);
NR12_REG = 0x00;
delay(50);
}

void G(){
NR12_REG = 0xF0;
NR13_REG = 0x50;
NR14_REG = 0x86;
delay(length);
NR12_REG = 0x00;
delay(50);
}

void A(){
NR12_REG = 0xF0;
NR13_REG = 0x78;
NR14_REG = 0x86;
delay(length);
NR12_REG = 0x00;
delay(50);
}

void B(){
NR12_REG = 0xF0;
NR13_REG = 0xA0;
NR14_REG = 0x86;
delay(length);
NR12_REG = 0x00;
delay(50);
}

void C(){
NR12_REG = 0xF0;
NR13_REG = 0xC8;
NR14_REG = 0x86;
delay(length);
NR12_REG = 0x00;
delay(50);
}

void D(){
NR12_REG = 0xF0;
NR13_REG = 0xF0;
NR14_REG = 0x86;
delay(length);
NR12_REG = 0x00;
delay(50);
}


void rest(){
delay(length);
}



void Song(){
while(1){
length = 500;
G();
length = 1000;
G();
length = 500;
E();
A();
length = 1000;
G();
length = 500;
E();
E();
length = 1000;
G();
length = 500;
E();
A();
length = 1000;
G();
E();
length = 500;
G();
G();
E();
length = 250;
E();
A();
length = 500;
G();
G();
E();
length = 250;
E();
A();
G();
G();
length = 500;
G();
E();
length = 250;
E();
A();
length = 1000;
G();
length = 500;
E();
length = 2000;
rest();
}
}

void main(){
printf(" \n\n\n\n\n\n\n  #SpaceKittyGames");
NR52_REG = 0x80;
NR51_REG = 0x11;
NR50_REG = 0x77;

NR10_REG = 0x00;
NR11_REG = 0x80;
NR12_REG = 0x00;
NR14_REG = 0x87;
Song();
}

Last edited by Crona (2014-10-21 16:04:28)

Oh cool thanks! I would never use this for an actual project, though. Just made the thing to become more familiar with the registers.

Wait couldn't I just do a #define for the names and the hex values?

To play a sampled sound on the gameboy is pretty simple. It's the same technique we used on the Commodore 64 back in the day.
Convert your sample (.wav file) to 4 bit at the rate you want to replay it at i.e. something the Gameboy can actually achieve.
Pass the 4 bit sample data to the volume register (which I think is 0-15, e.g. 4 bit) at the rate the sample was converted to.

Boom! You will be playing your converted wav file. Simples.

The Commodore 64/16/Plus 4 also had a mechanism in the cassette driver to detect 1s and 0s on the tape effectively giving you 1 bit samples. Very compact but very poor quality.